Device for testing the abrasion-resistance of surfaces of metallic articles



Aug. 30, 1960 W. J. CAMPBELL DEVICE FOR TESTING THE ABRASION-RESISTANCE OF SURFACES OF METALLIC ARTICLES Filed July 26, 1957 DEVICE FOR TESTING THE ABRASION-RESIST- AN CE F SURFACES OF METALLIC ARTICLES William J. Campbell, 38 Mair St., Glasgow, S.W. 1, Scotland Filed July 26, 1957, Ser. No. 674,375

2 Claims. (Cl. 73-7) The subject of this invention is a device for testing the abrasion or wear resistance of surfaces of metallic articles, more particularly hard anodic surfaces of articles of aluminium or of aluminium alloy.

The primary object of the present invention is to provide means for ascertaining readily the abrasionor wear-resistant properties of hard anodic coatings on aluminium or aired States Patent aluminium alloy articles of different shapes and dimensions.

A further object is to provide means for ascertaining the abrasionor wear-resistant properties of any anodic coatings on aluminium or aluminium alloy articles or of metallic coatings or surfaces on articles not necessarily form on the said surface superposed series of substantially equi-spaced zig-zag scratches of which adjacent scratches are spaced aparta distance of, say, 0.005 inch, the amount of material removed from said surfacebeing a measure of the abrasionor wear-resistance of said surface.

Each of the series of scratches may consist ofZO or scratches which made each be about 0.05 inch to 0.125 inch in length. In the testing of a hard-anodised surface on an aluminium article, an approximate measurement may speedily be obtained from the visual appearance of the surface after the formation of several, say 10, superposed series of scratches, the load on the stylus having been adjusted in such vise that a visible amount of debris from the abraded surface is deposited on the stylus. The abrasion resistance of two hard-anodised surfaces may then be compared as being in direct proportion to the number of superposed series of scratches necessary to produce the same amount of debris. A more precise measurement may be obtained if the actual depth of the scratches is measured after the formation of a selected number of superposed series of scratches. The abrasion resistance is then assessed in inverse proportion to the depth of the scratch, i.e., the softer is the surface, the deeper will be the scratch and vice versa.

A device for performing the method according to the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a side elevation of the device.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Referring to the drawings, 1 denotes the base of the device which is bored at 3 for mounting of the base 1 on an upright externally screw-threaded pillar (not illustrated) to provide for varying the height of the device from an article to be tested.

4 denotes an upright arm pivotally mounted on a fulcrum 5 for oscillatory movement through an arc of a few degrees. The arm 4 is normally urged in the direction towards a cam 6 by a tension spring 7 anchored at one end to the arm 4 and at the other end to a pin 8 upstanding from the base 1. The periphery of the cam 6 presents a plurality of equi-spaced teeth 6 A cam follower 6 in the form of a roller the axis of which is paralleel to that of the fulcrum 5 is mounted on the arm 4 to engage the periphery of the cam 6.

A substantially horizontal reciprocatory bar 9 pivoted intermediate its ends on a fulcrum 10 mounted in the arm 4 carries at one end a stylus 11. The other end portion of the bar 9 is pointed and is located adjacent to a microscope (illustrated diagrammatically at 12) adapted to measure the extent of vertical movement of the bar 9.

A cam follower 13 in the form of a roller the axis of which is substantially parallel to the bar is mounted on the arm 4 and is engaged with a cam 14 co-axial and in tegral with the cam 6. The arm 4 is slidably mounted on its fulcrum 5 and is normally urged by a compression spring 15 in the direction to engage the cam follower 13 with the cam 14. Both cams 6, 14 are integral with a wheel 16 mounted on a spindle 17.

In practice, when the spindle 17 is rotated at, say, '5 r.p.m., the wheel 16 and the associated cams 6, 14 also rotate; the follower 6 tracks the periphery of the cam 6 to effect oscillation of the arm 4 and reciprocation of the bar 9; and the follower 13 engaging the cam 14 causes reciprocation of the arm 4 transversely of the axis of reciprocation of the bar 9.

To test the abrasionor weanresistance of, for example, a hard-anodised surface, the device is positioned with the stylus 11 resting on the surface; a load such as a weight 9', on the arm 9 is adjusted sons to apply the desired load to the stylus 11; the positions of, for example, a marked tooth 6 of the earn 6, and of the point of the free end portion of the bar 9 are noted; and the'spindle 17 is rotated at constant speed for, say, 10 revolutions, until the cam assumes its identical original position.

During reciprocation of the bar 9 and of the arm 4,

the stylus 11 scores the surface to be tested with zig-Zag scratches and the pointed end portion of the bar 9 rises substantially vertically. After rotation of the spindle 17 has been stopped, the distance through which the point of the bar 9 has moved is measured by means of the microscope 12, the measurement being a measure of the Wear on the surface caused by the stylus 11.

The cam 14 is symmetrically formed as a cylinder intersected by a plane inclined to the axis of the cylinder. The cam 14 is co-axial with and secured to the cam 6 in such wise that both cams rotate simultaneously at the same angular velocity. The radial position of the cam 14 relative to the curved surface of one of the equi-spaced symmetrical teeth 6 determines the coincidence or otherwise of the superposed scratches produced by the stylus 11.

When the radius line of maximum axial projection of the cam 14 is angularly coincident with a radius on the cam 6 of the crest or the root of one of the teeth 6 the two cams 6, 14 may be said to be in a state of symmetry and the scratches of a pattern produced by the stylus 11 will be precisely coincident with the scratches of a preceding pattern on which said first-mentioned pattern is superposed because the reversal traversing action of the cam 14 at its maximum or its minimum limit on its follower 13 will cause the follower 6 of the cam 6 to retrace precisely its previous path whereas, when the radius line of maximum radial projection of the cam 14 is angularly coincident with a radius of the cam 6 which is equal in length to half of the radius of the earn 6 to the crest plus half' asymmetrical condition is preferable for .visual assessment of the wear as there is then more break-up of thesurface.

material where the scratches cross one another..

The cams 6, 14 maybe so arranged that the relative rates of reciprocation of. the bar 9 and .of the arm 4 are approximately 40,21. Thus, if the cam 6 reciprocates the bar 9 at 200 strokes per minute, .the cam 16 will reciprocate the arm 4 at 5 strokes per minute.

The amplitude of reciprocation of the arm 4 is related to the dimensions of the point of .the stylus 11 which may be constitutedlby a diamond or a sapphire pyramid or by a metallic needle or a pointed abrasive member.

During reciprocation of the bar 9, the stylus 11 .will score a V-shaped groove in the surface being tested. To avoid undue protraction of the time taken for the test, the load on the stylus 11 is adjusted so that the rims of adjacent grooves are close to one another after only a few reciprocations of the bar 9. e

As the depth of thesurface removed by wear during the test is usually of the order of 0.0001 inch and the area tested-is of theorder of 0.01 square inch, the test does not render the surface unserviceable and can readily be used in connection with a relatively small article, such as a spindle having a diameter of A of an inch, or with "a tube the internal diameter of which is of the order of r such as inverting thestylus from the direction illustrated, 7

increasing the length of the vertical arm- 4- beyond the length illustrated and reversing the direction of the load on the stylus.

In order to establish a relationship between the measurement of surface hardness efiected by the device according to the invention and conventional'devices for measuring surface hardness, a diamond pyramidal stylus is traversed a few times under a predetermined load over a steel surface of known Brinell or Rockwell hardness and the depth of the score produced on the steel is measured. The same stylus under the same load is then traversed the same numberof times over a hard-anodised surface to be-tested andthe'depth of-the score produced is again measured. The measurement of the hardness of the anodic coating is then related to the Brinell or Rockwell hardness number obtained in ,connection with the test on the steel.

While the device has been primarily adapted to measure the abrasion resistance of hard-anodic coatings, it may also be usedfor measuring the hardness of ordinary anodic coatings or indeed of thin surface layers on articles not necessarily consisting of aluminium or aluminium alloy by adjusting the load on the stylus to one which will cause the stylus to produce scores of a .depthconsiderably less thanthe thickness of the surface layer.

What is claimed 1. A device for testing'the abrasion-resistance of coatings produced electro-chemically. on metallic articles, including a bar, a stylus connected to one .end of said bar, and means connected to said bar intermediate its ends for effecting relatively rapid reciprocation of'sa'id bar in one direction in a substantially horizontal plane and relatively slow reciprocations in the same plane in a direction transversely of the axis of .reciprocation in said first direction, said bar and associated stylus being free to oscillate in a vertical plane.

2. A device as claimed in claim 1, in which the bar is pivoted intermediate its ends to a substantially upright arm pivotally mounted on a fulcrum, and cam means is operable ,to oscillate ,said bar about the axis ofsaid fulcrum and toreciprocate on :said fulcrum. I

References Cited in the file of this patent UNITED STATES PATENTS Galbraith et al. Feb. 14, 1956 

